1. superlative form of rare; most uncommon or infrequent
2. superlative form of rare; most valuable or precious due to scarcity

Examples

• This is the rarest coin in my collection.
• The rarest birds are found only in remote forests.
• She owns one of the rarest books ever printed.
• The rarest gems command the highest prices.
• Finding a four-leaf clover is among the rarest of luck.
• The museum displays the rarest artifacts from ancient civilizations.